Low-density polyethylene (LDPE) leads to serious environmental problems because it is one of the widely used plastic materials in the packaging industry. It is well known that LDPE can be made degradable by blending it with biopolymers and pro-oxidants but some recent studies reported nanoclay can also help although only in photo-degradation. The present study aims to investigate the effect of nanoclay on the photo-degradation and biodegradation of polyethylene.

LDPE-nanoclay composites (nanocomposites) were prepared by melt intercalation technique using different clay concentrations. Photo-oxidation, which is usually the initial stage in biodegradation, was achieved by exposing the nanocomposite films to UV irradiation in a weatherometer. Following that, biodegradation was achieved by inoculating the microorganism Pseudomans aeruginosa on photodegraded films. The biofilm formed during the biodegradation was observed by environmental scanning electron microscopy. The changes in the molecular weight and the concentration of oxidation products formed during the photo-oxidation and biodegradation were monitored by gel permeation chromatography and Fourier transform infrared spectroscopy, respectively.

The decrease in the concentration of carbonyl compounds with time and the formation of biofilm on polymer film indicates the progress of biodegradation. The rate of biodegradation is greater for irradiated polyethylene and its nanocomposites as compared to that for non-irradiated samples. This is mainly because the high molecular weight polyethylene molecules break into low molecular weight fragments during the photo-oxidation leading to the production of substrate that is suitable for bacterial growth. Also the rate of molecular weight reduction increases with the increase in clay concentration.